Added new kb article resolving-excel-file-corruption-warning-after-spreadprocessing-export

knowledge-base/resolving-excel-file-corruption-warning-after-spreadprocessing-export.md

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+---
+title: Fixing Corrupt Excel Files After Export Using Telerik SpreadProcessing
+description: Resolving issues where exported Excel files using Telerik SpreadProcessing show corruption warnings after upgrading to version 2025.2.520.
+type: how-to
+page_title: Resolving Excel File Corruption Warning After SpreadProcessing Export
+meta_title: Resolving Excel File Corruption Warning After SpreadProcessing Export
+slug: resolving-excel-file-corruption-warning-after-spreadprocessing-export
+tags: telerik-document-processing, spreadprocessing, excel-export, memory-stream, corrupted-file
+res_type: kb
+ticketid: 1695962
+---
+
+## Environment
+| Version | Product | Author | 
+| ---- | ---- | ---- | 
+| 2025.2.520| RadSpreadProcessing |[Desislava Yordanova](https://www.telerik.com/blogs/author/desislava-yordanova)| 
+
+## Description
+
+Exporting an Excel file using Telerik SpreadProcessing shows a corruption warning when opening the file in Excel. This issue occurs when reusing the same `MemoryStream` for both import and export operations without resetting or truncating the stream. The problem started after upgrading to version 2025.2.520 due to changes in the library that replaced `Telerik.Zip` with `System.IO.Compression`. 
+
+This knowledge base article also answers the following questions:
+- How to fix "Excel found unreadable content" errors after export?
+- Why does my exported Excel file open with a corruption warning?
+- How to resolve MemoryStream issues with Telerik SpreadProcessing?
+
+## Solution
+
+To ensure the exported files are not corrupted, reset or truncate the `MemoryStream` before export, or use a new stream. Follow these steps:
+
+1. **Reset and Truncate the Stream:**
+   Before exporting, truncate the `MemoryStream` to remove residual content and reset its position. Use the following code:
+
+   ```csharp
+   XlsxFormatProvider formatProvider = new XlsxFormatProvider();
+   using (Workbook workbook = formatProvider.Import(memoryStream))
+   {
+       memoryStream.SetLength(0);    // Truncate stream to remove previous content
+       memoryStream.Position = 0;    // Reset position to start
+       formatProvider.Export(workbook, memoryStream);
+       formatProvider = null;
+   }
+   ```
+
+2. **Use a New MemoryStream for Export:**
+   Alternatively, create a new `MemoryStream` for exporting to avoid residual data issues:
+
+   ```csharp
+   XlsxFormatProvider formatProvider = new XlsxFormatProvider();
+   using (Workbook workbook = formatProvider.Import(memoryStream))
+   {
+       using (MemoryStream newMemoryStream = new MemoryStream())
+       {
+           formatProvider.Export(workbook, newMemoryStream);
+           // Use newMemoryStream for further processing
+       }
+       formatProvider = null;
+   }
+   ```
+
+### Additional Notes:
+- If you are not explicitly using the [RadZipLibrary](https://docs.telerik.com/devtools/document-processing/libraries/radziplibrary/overview), you can safely remove its reference in your project. Starting with version 2025.2.520, Telerik Document Processing Libraries use `System.IO.Compression` internally.
+
+## See Also
+
+- [Telerik SpreadProcessing Documentation](https://docs.telerik.com/devtools/document-processing/libraries/spreadprocessing/overview)
+- [RadZipLibrary Documentation](https://docs.telerik.com/devtools/document-processing/libraries/radziplibrary/overview)
+- [Release Notes for Telerik Document Processing Libraries 2025.2.520](https://www.telerik.com/support/whats-new/telerik-document-processing/release-history/progress-telerik-document-processing-2025-2-520-changelog)